Tuesday, 18 June 2019

Ribbed and lubricated, how to slide without wood.


Stone 59

How the stones of Stonehenge were dragged to the site is of constant fascination. The title of this note was a scribbled message I left myself that I had to remember what I was thinking about late at night when I wrote it.

On Orkney excellent work was done showing how lubricated ground worked better than rollers under a moving monolith - http://brodgar.co.uk/2016/07/10/how-do-you-move-a-standing-stone/ .
They used seaweed but dewey or rotting cut grass on hard ground is like ice as I know to my cost.

Flat stones have a high drag factor and also slide sideways on any cross slope, so just throwing an idea out there would ribbed stones, like the strakes on a boat's hull, reduce friction and provide directional stability?

Could it have been done without the rollers, or sledges and frames we presume were needed?





Wednesday, 15 May 2019

Stonehenge Parchmarks 17 18 19 20

When the parchmarks of 2013 showed up I crept onto site one morning with a stepladder and ranging rod to take some close vertical photos.  The size and shape of the parchmarks strongly suggests that they were for stones rather than just marker posts used to set out the circle, I think.





Recording the parchmarks 



The first photo taken



Stonehole 17



Stonehole 18



Stonehole 19



Stonehole 20



Tuesday, 14 May 2019

The consistent, not "warm", springs of Blick Mead


David Jacques describing Blick Mead "The springhead and springline water temperature is a steady 10-13 ºc all year. The experiments that confirmed this observation were conducted by Pete Kinge of QinetiQ using fixed thermal imaging cameras and by Tim Roberts."




This steady consistent temperature provides the useful property of unfrozen water for drinking by the wildlife as well by humans and also encourages early grass growth for grazing. Blick Mead would have been one of the larger such spring fed pools in the area. The consistent temperature in a grove of trees would also provide for the panting hart cool water and shade in the summer.





But these are not "warm" springs as usually understood. Warm springs or thermal springs are those where hot water from great depths in the Earth rises to the surface. Blick Mead's springwater is at the normal temperature of groundwater, with maybe a slight increase in temperature over neighbouring springs as the water is coming from under a greater depth of chalk than at them as the land rises steeply directly behind Blick Mead. (Groundwater temperature varies with depth - the ground temperature shows seasonal fluctuations to depths of about 15 m where the temperature is approximately equal to the mean annual air temperature(8 - 11° C in the UK). Below this the ground temperature increases at, on average, 2.6 °C per 100 m due to heat flowing from the interior of the Earth. Mean temperatures at 100 m depth in the UK vary between about 7 - 15°C.)


Webb, B. W. and Zhang, Y. (1999), Water temperatures and heat budgets in Dorset chalk water courses. provides a good understanding of similar waters and references for further research.

"Two reaches were investigated in this study. The reach on the tributary of River Piddle at Wateston Manor, Dorset, UK (National Grid Reference SY 723956) was located  c 10 m below the main spring which feeds this watercourse. ... The River Bere at Bere Heath. Dorset, UK is a larger water course which is underlain almost entirely by upper chalk. It rises in a number of springs and is fed by a borehole, and most of the How passes through watercress beds in the upper reaches. The channel in the study reach (National Grid Reference SY 723956) flows through cattle ….Measurements were made on a total of 28 days in February and March, 1994 and 12 days in July. 1994"



But there is a hint that there might actually be thermal springs nearby.

Just up river from Blick Mead is the site of English Heritage's first choice for a Stonehenge Visitor Centre - the planning documents have a wealth of Archaeological and geological information. 

"The chemistry of the groundwater has been analysed in one sample obtained from BH8. The results of this indicate that the water has a pH value of 6.7 a temperature of 16.2°C, conductivity of 780µS/cm a total hardness of 338mg/l and a saturation of -42mg/l.
In consideration of these results the temperature of the groundwater at this location was unexpectedly high...." 
Appendice A10.4 - Extract From Geotechnical InvestigationsReport On Groundwater Conditions 

Details of the testing are hard to find but it seems to have been taken in the spring and there is a suggestion that the groundwater is being contaminated by rain  falling on the surface stripped area. But even it is only one sample the "unexpectedly high" temperature of the groundwater near Blick Mead is intriguing.


Tuesday, 9 April 2019

Has Mike Pitts found the last missing stonehole?

On Twitter:






Mike Pitts @pittsmike Apr 7

The promo video for a #Stonehenge exhibition in Kansas City includes an extraordinary aerial film clip showing the best photographic record I’ve seen of the parch marks revealed in summer 2013. https://www.unionstation.org/stonehenge/index.php


Tim Daw @TimothyDaw 7:33 AM - Apr 9, 2019

@pittsmike you have spotted Stone 24 (possible) stone hole - I have looked at lots of aerial shots and not seen it. In 2013 I looked hard for it and couldn't see it, ony could imagine it. Congratulations.



Sunday, 31 March 2019

Concrete Prehistories: The Making of Megalithic Modernism

Concrete Prehistories: The Making of Megalithic Modernism

Helen Wickstead, Martyn Barber
Issued Date: 2 Sep 2015

Abstract


After water, concrete is the most consumed substance on earth. Every year enough cement is produced to manufacture around six billion cubic metres of concrete . This paper investigates how concrete has been built into the construction of modern prehistories. We present an archaeology of concrete in the prehistoric landscapes of Stonehenge and Avebury, where concrete is a major component of megalithic sites restored between 1901 and 1964. We explore how concreting changed between 1901 and the Second World War, and the implications of this for constructions of prehistory. We discuss the role of concrete in debates surrounding restoration, analyze the semiotics of concrete equivalents for the megaliths, and investigate how concreting became meaningful in interpretations of prehistoric building activities. The archaeology of megalithic concrete illustrates the untimeliness of concrete as a technology that entangles ancient and modern.

Download 

https://eprints.kingston.ac.uk/33941/1/Wickstead-H-33941-AAM.pdf

Tan Hill Experimental Firing Range

In the 1950s there was an experimental artillery firing range on the Marlborough Downs - Gunsight Lane in West Kennet is presumably named after its use or construction for the range. On Tan Hill there were telegraph posts running along the Wansdyke and what I remember as a flag pole. There was also a strange thick (two or three inches) iron plate that had been used as a target. Seeing two inch holes through it impressed me as a child.

31 March 2019 - I was pleased to find a pole, the plate and the concrete base of the scaffold all still there.

Plate, concrete base and the top of Silbury Hill in alignment.













The concrete plinth on Google Maps


Tuesday, 15 January 2019

Chubb's 400 yard Mystery

When Cecil Chubb gifted Stonehenge he put some conditions in the Deed , the third one was;

Thirdly that no building or erection other than a pay box similar to the Pay Box now standing on the premises shall be erected on any part of the premises within four hundred yards of The Milestone marked “Amesbury 2” on the northern frontage of the premises.

I have wondered why, and if I have been told I can no longer remember, did he stipulate a a 400 yard radius circle rather than just say "within the premises"?



A quick sketch shows his 400 yards almost covers the whole of his gifted land apart from the tips of two corners. Is that deliberate?

Of course within a few years the curators houses had been built with in the 400 yards so it appears his wishes were ignored from the earliest of days.

And ironically he chose the one stone in the landscape that was then moved, to the other side of the road.

The Deed - http://www.sarsen.org/2013/12/cecil-chubbs-deed-of-gift-of-stonehenge.html